With increasing popularity of an Internet communications technology, various distributed storage systems, such as a web disk and a cloud storage system, are gradually used by more users. In a distributed storage system, a bandwidth resource and a server resource are limited. How to better protect a benefit of a developer of a distributed storage system and how to create good user experience for a user are considered hot issues. Downloading a file from the distributed storage system by a terminal is limited by using access permission so as to implement a function of link theft prevention; for example, conditions, such as a requesting source of a download request, a client, an IP (Internet Protocol, Internet Protocol) segment, and a download validity period may be determined to avoid link theft.
In the prior art, download permission is stored in a server. When a file is being downloaded, a download access node needs to send a download request to the server so that authentication is performed by the server, or a download access node needs to request the download permission from the server so as to complete authentication. In this case, in an authentication process, not only load on the server increases, but also an authentication speed and a response speed for downloading a file are reduced.